Tom W8JI wrote:
> ...
>
> Also there is a basic flaw with two-tone tests. Two-tone
> tests don't vary the power supply loading like a voice
> signal would. Flaws in grid voltage or high voltage dynamic
> regulation may not show at all. Almost always the error
> makes things look better than they really are.
> ...
>
Thinking a little more about the dynamic IMD with syllabic fluctuations,
etc., I wonder if a narrow spaced two-tone test (10 to 30 Hz, ala
PSK31) would be a useful proxy. The low-frequency beat would test
supply regulation, as others have noted.
I'm not sure I've ever seen numbers relating to dynamic linearity - just
the simple wide spaced two-tone tests. Do we have results, or are these
just suspicions?
Plate supply regulation is not very good in most amps, it seems.
Something like -30% no load to full load? This must have an impact, but
it's not obvious how much it affects IMD, or how you would measure it.
73, Martin AA6E
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